Brown — Permanent Steel Magnets. 



319 



12 per cent of tungsten has made an increase of 65 per cent, in tlie magnetic 

 moment, and iiici'eased the retentivity nearly three times. 



In the chrome steels Nos. 13 and 14, the lower percentage of chromium 

 seems to have a better effect on the moment than the higher, as is also 

 indicated in No. 5, though when nickel is present, as in Nos. 15 and 16, it 

 appears to mask the effect of eliromium if the amount of the latter is small. 



Abt' has published some results on the comparison of tlie magnetic 

 moments of magnets, which have the same dimensions, and magnetized in 

 the same magnetic field, but of different composition, tliat is, crucible, 

 diamond, and tungsten steels. The magnetic moments of these magnets 

 were 33'7, 35'9, and 62'15, and at the end of the four months the percentage 



losses were I'l, 25"9, and 26'5 respectively. The last value is very high for 

 tungsten steel ; the chemical composition of the steels, however, is not given in 

 the paper. Mme. Curie,^ in an important paper on the magnetic properties 

 of tempered steels, where most of the specimens tested were in the form of 

 bars of square section 20 cms. long and one centimetre in the side, gives the 

 results of some tests on tungsten steels. If we take the steels with the 

 highest and lowest amounts of tungsten mentioned in the paper, and assume 

 the density of the material to be 8, we find the magnetic moment per 

 gramme to be 63 for the steel with W = 2'7, and 45 for that with W = 7'7. 

 The results for the four best specimens in Table IV., namely, the two 

 tungsten steels (Nos. 9 and 10), and the two chrome steels (Nos. 13 and 14), 

 are shown in curves in fig. 3, which exliibits the behaviour of each specimen 



1 Wied. Ann. Ixvi. 1, pp. 116-120, 1898. 



2 Bull, de la Societe d' Encouragement, pp. 36-76, 1898. 

 SCIENT. PKOC. K.D.S., VOL. XII., NO. XXVI. 



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